Android scrollview 在片段事务后保持滚动 position

Question

I want to keep scrollview scroll position of a fragment. This fragment ( HomeFragment.kt ) is one of several fragments within a fragment with bottom navigation ( DashboardFragment.kt ).

This is how HomeFragment.kt loaded (This is a snippet of DashboardFragment.kt )

    private fun loadHomeFragment() {

        homeFragment = HomeFragment()

        dashboardFragmentManager.beginTransaction()
            .setCustomAnimations(
                android.R.animator.fade_in,
                android.R.animator.fade_out
            )
            .replace(R.id.content, homeFragment, "1")
            .commit()
    }

And this is the scrollview layout (This is a snippet of HomeFragment.kt layout):

    <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/swipeBaseLayout">

            <ScrollView
                android:id="@+id/baseLayout"
                android:layout_width="match_parent"
                android:layout_height="match_parent">

                <RelativeLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    android:paddingBottom="32dp">

                    <com.synnapps.carouselview.CarouselView
                        android:id="@+id/carouselView"
                        android:layout_width="match_parent"
                        android:layout_height="300dp"
                        app:fillColor="#FFFFFFFF"
                        app:pageColor="#00000000"
                        app:pageTransformInterval="800"
                        app:radius="3dp"
                        app:slideInterval="5000"
                        app:strokeColor="#FFFFFFFF"
                        app:strokeWidth="1px" />


                    <RelativeLayout>
                       .....
                    </RelativeLayout>

                </RelativeLayout>
            </ScrollView>
        </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>

As you can see, I already have an id for the scrollview. But every time this fragment loaded or navigated back from another fragment (From another fragment to DashboardFragment.kt ) (I'm using navigation component), it'll start from the top.

Is there any way to keep scrollview even after the fragment transaction? If there's any detail I missed to point out, just let me know.

Answer 1

For more control on your backstack, you can have your custom stack and check there is only one instance of a fragment in the stack. Also for your problem, you can hide other fragments that are on top of the stack:

   showFragment(Fragment homeFragment) {
    fragmentTransaction = fragmentManager.beginTransaction();
    for (int i = 0; i < fragmentManager.getFragments().size(); i++) {
        if (fragmentManager.getFragments().get(i) != homeFragment) {
            fragmentTransaction.hide(fragmentManager.getFragments().get(i));
        }
    }
    fragmentTransaction.show(homeFragment);
    fragmentTransaction.commit();
}